1. Industrial Field of the Invention
The present invention relates to a liquid crystal display device, particularly one provided with a retardation film for eliminating coloring caused on the liquid crystal display panel, and an electronic device such as a watch or a portable telephone using such a liquid crystal display device.
2. Description of the Related Art
There is conventionally known a liquid crystal display device provided with a liquid crystal display panel such as an STN (Super-Twisted Nematic) liquid crystal, in which a retardation film such as a uniaxial drawn film is arranged on one side of the liquid crystal display panel (for example, see Japanese Examined Patent Publication No. 3-50249 previously proposed by the present inventors).
FIG. 9 is a descriptive view of a schematic configuration illustrating an example of the conventional liquid crystal display device provided with the retardation film as described above. In FIG. 9, 1 is an upper polarizer; 2 is a retardation film; 3 is a liquid crystal display panel; 4 is a lower polarizer; and 5 is a reflector. The liquid crystal display panel 3 has a pair of upper and lower substrates 31 and 32 holding a liquid crystal layer 33 there between.
As the above-mentioned retardation film, uniaxially drawn polymer film such as a polycarbonate film is used. Coloring produced on the liquid crystal display panel is eliminated by appropriately selecting a material and a thickness of the retardation film in response to the product of multiplication .DELTA.n.multidot.d of the anisotropy of refractive index .DELTA.n of the liquid crystal display panel and the thickness d of the liquid crystal layer and other parameters. While FIG. 9 illustrates a reflective liquid crystal display device, a backlight is installed in place of the reflector 5 in a transmissive liquid crystal display device.
However, use of a retardation film as described above did not always ensure sufficient elimination of coloring caused by the liquid crystal display panel, and particularly, it was difficult to eliminate coloring in both the ON-state and OFF-state.
The results of extensive studies on these problems revealed that coloring was further accelerated by the reflector. More specifically, as shown in FIG. 10 illustrating spectroscopic properties of an aluminum reflector commonly in use in conventional liquid crystal display devices, reflectivity is higher in the high-wavelength region than in the low-wavelength region of the visible light region, and this is accelerating coloring.
The present invention was developed in view of these problems and has an object to provide a liquid crystal display device using a retardation film as described above, which satisfactorily and certainly eliminates coloring in the ON-state as well as in the OFF-state and gives a good contrast, and an electronic device using the same.